You're probably going to hear this from others, but get some insurance quotes. I'm a CFII that took a reinstatement ride about 18 months ago. Since then I've used my Citabria for some dual instruction (tail wheel endorsements and flight reviews). I did it "at risk" that as owner and PIC that any runway excursion that resulted in damage would be my responsibility. Not a scratch.

Many years ago I ran a one man flight school and owned a Cardinal RG. I well remember the day I transitioned from $1000/year for my personal use to $1100/month for insurance that would allow dual instruction and renting. Obviously the plane has to fly quite a bit to pay for that.

After doing about 4 tail wheel endorsements in my Citabria I inquired with my insurance broker about going legit, and asked for a quote that would cover dual instruction only (no rental. no way am I getting back into that game). My $560/year policy would turn into $4k. I penciled it out and I would have to bump my rate from $155/hr dual to $200/hr and instruct at least 40 hours/year, otherwise all I would be doing is subsidizing other people's flying. I'd like to think I'm a nice guy but not that nice.

So call it at least four tail wheel endorsements/year. Now I might average that or slightly more, but this would force me to seek out students where up until now I've just used word of mouth referrals. I love instructing way more than I love my day job but I've done it for a living and I can affirm it is a more austere lifestyle, so if it is anything more than a hobby it is just going to interfere with my personal flying (and building) schedule.

I will say it would be a nice niche with lots of potential customers, so if you go this route then good on you.

Word to the wise: You need to emotionally detach yourself from any aircraft that is on the line for rent. It is a business asset, end of story. Like owning a pop machine or piece of restaurant equipment. Otherwise you're going to lose your s*** about once per week at how your baby is treated.